Practical

Question 1

What is Biuret’s test for

Answer 1

Proteins

Question 2

What is Benedict’s test for

Answer 2

Reducing sugar

Question 3

What is Iodine test for

Answer 3

Starch

Question 4

What is ethanol emulsion test for

Answer 4

Fats

Question 5

How to carry out Biuret’s test

Answer 5

• Add 1cm^1 of sodium hydroxide solution to 2cm^3 of food solution
• Shake thoroughly
• Add 1% copper(II)sulfate solution drop by drop, shaking after each drop until colour change observed

Question 6

How to carry out iodine test

Answer 6

• Place food substance or solid food onto white tile
• Add a few drops of iodine solution to substance and observe colour change

Question 7

How to carry out Benedict’s test

Answer 7

• Add equal volume of Benedict’s solution to 2cm^3 of food solution in a test tube
• Shake mixture thoroughly
• Place test tube in a boiling water bath for 5 minutes
• Observe precipitate formation and colour changes

Question 8

How to carry out ethanol emulsion test

Answer 8

• Add 2cm^3 of ethanol to 2cm^3 of food solution in a test tube
• Shake mixture thoroughly
• Decant ethanol mixture into another test tube containing 2cm^3 of water

Question 9

Observations and conclusions if no reducing sugars present

Answer 9

• Solution remained blue
• No reducing sugars present

Question 10

Observations and conclusions if little concentration of reducing sugars present

Answer 10

• Green precipitate formed
• Little concentration of reducing sugars present

Question 11

Observations and conclusions if moderate concentration of reducing sugars present

Answer 11

• Yellow precipitate formed
• Moderate concentration of reducing sugars present

Question 12

Observations and conclusions if large concentration of reducing sugars present

Answer 12

• Orange or brick-red precipitate formed
• Large concentration of reducing sugars present

Question 13

Observations and conclusions if proteins present

Answer 13

• Violet colouration observed
• Proteins present

Question 14

Observations and conclusions if proteins absent

Answer 14

• Solution remained blue
• Proteins absent

Question 15

Observations and conclusions if starch present

Answer 15

• Blue black colouration observed
• Starch present

Question 16

Observations and conclusions if starch absent

Answer 16

• Solution remained brown
• Starch absent

Question 17

Observations and conclusions if fats present

Answer 17

• White emulsion formed
• Fats present

Question 18

Observations and conclusions if fats absent

Answer 18

• Solution remained colourless
• Fats absent

Question 19

How to increase reliability of an experiment

Answer 19

Repeat experiment a few more times and find the average values

Question 20

How to increase accuracy of experiment

Answer 20

Use more accurate apparatus

Question 21

Graph plotting is what against what

Answer 21

Plot a graph of y against x

Question 22

Things to do for planning exercise

Answer 22

• Identify aim of experiment
• Identify independent, dependent, and constant variables
• Specify at least 5 different, regular intervals for independent variable
• Specify what graph to plot
  Conclusions:
• If what happens, then what happens (Relate back to aim of experiment)